The present invention relates to filter cartridges for fluids and more particularly to high surface area, replaceable filter cartridges for gas or liquid filtration applications.
Efforts to increase the effective filter area while minimizing filtration unit size have led to a variety of filter arrangements in which a flat filter sheet is folded into pleated structures.
In U.S. Pat. No. 2,683,537, a generally cylindrical filter cartridge is produced from a flat paper filter sheet in which the connecting area between pleats has a series of tucks which allow the course of the pleats to be reversed without cutting the filter paper.
Alternative pleated structures for a filter cartridge are disclosed in U.S. Pat. No. 2,897,971 and U.S. Pat. No. 3,087,623, where a multiplicity of pleated cylindrical elements are interconnected by adhesively or mechanically bonding the free edges of adjacent elements together.
A more conventional approach to increasing the available filtration area while minimizing the volume of the filter unit involves the use of longitudinal, accordion pleats wherein the filter media is folded into a pleated structure and formed into a generally cylindrical shape. U.S. Pat. No. 3,867,294 and EP 44,042 disclose two of many variations of this basic concept.
Another approach to increasing the surface area of filter cartridges involves the formation of a series of disk filter layers in a stacked configuration is disclosed in U.S. Pat. No. 4,594,162. In this structure, the filter media is formed around a mandrel by means of a pneumatic pleating operation to produce a high density stacked disk layer filter.